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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [ Nokia PHY submission to Task Group 4 ] Date Submitted: [ 07 May, 2001 ] Source: [ Jukka Reunamäki ] Company [ Nokia ] Address [ Visiokatu 1, P.O.Box 100, FIN-33721 Tampere, Finland ]

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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Nokia PHY submission to Task Group 4] Date Submitted: [07 May, 2001] Source: [Jukka Reunamäki] Company [Nokia] Address [Visiokatu 1, P.O.Box 100, FIN-33721 Tampere, Finland] Voice:[+358 7180 35331], FAX: [+358 7180 35935], E-Mail:[jukka.reunamaki@nokia.com] Re: [Original document] Abstract: [Submission to Task Group 4 for consideration as the Low Rate PHY for 802.15.4] Purpose: [IEEE 802.15.4 PHY proposal for evaluation] Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15. Jukka Reunamäki, Nokia

  2. Nokia PHYsical layer submission to IEEE 802.15 Task Group 4 Presented by Jukka Reunamäki Nokia Jukka Reunamäki, Nokia

  3. Contents • Cost and power consumption requirements • Operation frequency band and channel structure • Bit rate, modulation and performance • Link budget • Susceptibility to interference • Implementation examples • Conclusions • Self-evaluation against criteria Jukka Reunamäki, Nokia

  4. General PHY requirements • Minimized RF and BB complexity • Very low cost • Strongly minimized power consumption • Relaxed performance requirements • Unlicensed operation frequency band • FCC and ETSI compliance • Mature, low risk approach Jukka Reunamäki, Nokia

  5. Cost requirements • Target applications necessitate sub-dollar solutions • Addition of WPAN capability should not increase total cost of the solution notably • Minimized number of components • Single-chip or dual-chip implementations • Only few external components • Mature, bulk RF and/or digital IC processes to be used • Cost optimum most probably differs from power consumption and size optima Jukka Reunamäki, Nokia

  6. Power consumption and operation time • Idle time power consumption assumed to be 1/1000 of power consumption in active mode. Jukka Reunamäki, Nokia

  7. Implications of power consumption requirements • Transceiver should consume about 10-25 times less power than current Bluetooth approaches to be feasible for button batteries • It is possible with very low duty cycles (<< 1%) • In active mode the whole transceiver including digital processing should consume only ~4 mW with small button cell and ~12 mW with large button cell • Idle time dominates power consumption in case of low duty cycles • Synthesizer is also critical Jukka Reunamäki, Nokia

  8. Spread spectrum vs.narrowband • Basically, SS does not provide any benefit against interference in the 2.4 GHz ISM band • Though, SS enables higher TX powers and faster synchronization • Narrowband system is more seldom hit by Bluetooth transmission • Narrower signal bandwidths signify lower sampling rates and smaller power consumption • More non-overlapping channels in the system band • Less complex baseband Jukka Reunamäki, Nokia

  9. Operation frequency band • Default is 2.45 GHz ISM band • Unlicensed, global and congested • Quite high frequency from minimum implementation and propagation point of view • Operation under FCC 15.249 (US) and ERC rec 70-03 SRD (Europe) • Optional bands: 902-928 MHz in US and 433.050 - 434.790 MHz in Europe • Smaller propagation loss, potentially less interference • Any band wide enough and available for short-range devices can be used Jukka Reunamäki, Nokia

  10. Channel structure in 2400-2483.5 MHz • 83 channels, center frequencies at 2401 + k x 1 MHz, where k = 0...82 • Compatibility with Bluetooth • Outermost channels benefitially located IEEE 802.11b channel in North America and Europe Bluetooth channels Channels of the proposed system IEEE 802.11b channel in Europe 2480 2401 2402 2403 2481 2482 2483 2400 Jukka Reunamäki, Nokia

  11. Device classes for different applications • Smaller TX power => smaller operating space and power consumption • Fixed frequency => potentially simpler implementation • Generally, sensitivity is not the dominant item from power consumption point of view if the requirements are reasonable (i.e. NF  15) • Communication between different classes is possible Jukka Reunamäki, Nokia

  12. Bit rate and modulation • Maximum physical layer bit rate 200 kbps • Data rate scalability achieved with lower activity, shorter packets and possible repetition coding • Long symbol duration results in small ISI in indoor channels • 200 kbps aggregate capacity considered adequate from application point of view • 2GFSK modulation with modulation index h = 2...3 and BT = 0.5 • Constant envelope for low power TX architecture • Spectrum efficiency sacrificed for minimum complexity and low power RX implementation • Relaxed requirements for phase noise, I/Q imperfections and frequency drift Jukka Reunamäki, Nokia

  13. Modulation spectrum 2GFSK modulation with modulation index h = 2.5, BT = 0.5 Jukka Reunamäki, Nokia

  14. Transmit spectrum with different modulation indexes Jukka Reunamäki, Nokia

  15. Performance in AWGN channel C/NBER = 1e-3 = 13.5 dB C/NBER = 1e-4 = 15.0 dB C/NBER = 1e-3 = 13 dB C/NBER = 1e-4 = 14.5 dB 2GFSK, modulation index h = 2.5, BT = 0.5, f-3 dB, highpass = 50 kHz, f-3 dB, lowpass = 300 kHz Jukka Reunamäki, Nokia

  16. Performance in multipath channel: ISI • The exponentially decaying fading channel model defined in criteria document: • Assumes at least four samples per symbol • Sufficient number of fading taps = 10*TRMS/Ts • For the 200 kbps data rate with 4 samples per symbol the channel is flat fading when the delay spread is smaller than 250 ns Jukka Reunamäki, Nokia

  17. Performance in flat fading Rayleigh channel X % signifies that raw BER is equal to or better than that indicated by the curves at a corresponding C/N value in X % of flat fading Rayleigh channels. Jukka Reunamäki, Nokia

  18. Channel coding • By default no channel coding of any kind utilized • Coding does not help much when the transmitted frame is overlapped by high power interference in both frequency and time • Increases baseband complexity • No need to extend range by means of coding • Real-time services are not in focus • Data reliability ensured by 32-bit CRC checks (providing error detection up to BER  1e-9) and upper layer retransmissions • If needed, repetition coding can be used Jukka Reunamäki, Nokia

  19. Link budget at 2.45 GHz Fading margin of 13 dB ensures that C/N = 14.5 dB or better in > 95% of the channels at range of 25/10/3/1 m. Jukka Reunamäki, Nokia

  20. Example: link budget of unbalanced link with directive antenna • A link formed between devices with different capabilities e.g. based on power supply constraints Jukka Reunamäki, Nokia

  21. Scalability • Range • More range can be achieved by means of higher TX power (only -10 dBm proposed) • FCC 15.249 addresses average power! • Low duty cycles => high TX powers possible • Data rate • Scalability implemented through packet sizing and duty cycles • Frequency band of operation • Narrow transmit bandwidth basically allows usage of a number of different frequency bands, e.g. 433 MHz (Europe), 868 MHz (Europe), 915 (US), 2.4 GHz (global) Jukka Reunamäki, Nokia

  22. Susceptibility to interference • 2.45 GHz ISM band will be congested • Low power system cannot compete with TX power • Relaxation in interference susceptibility accepted to alleviate RX linearity requirements • RX linearity requirements similar to Bluetooth (IIP3 = -15...-20 dBm) would not result in low-power RX, since RX linearity directly affects power consumption • In case of co-channel interference, strong adjacent channel interference, blocking or intermodulation, packets are retransmitted Jukka Reunamäki, Nokia

  23. Co-channel and adjacent channel interference Jukka Reunamäki, Nokia

  24. CW interference • Note: CW interferer @ 0 Hz offset does not deteriorate performance due to highpass filtering in zero-IF RX! Jukka Reunamäki, Nokia

  25. IMD C/I Intermodulation resistance • Values • IIP3 = -30 dBm • C/IBER = 1e-4, sensitivity + 3 dB = 10 dB • PCW interferer = -51 dBm Jukka Reunamäki, Nokia

  26. Intermodulation resistance – a strong function of IIP3 Bluetooth TX Bluetooth TX RX TX IMD C/N Jukka Reunamäki, Nokia

  27. RX IIP3 vs. relative supply current Jukka Reunamäki, Nokia

  28. Bluetooth interference Jukka Reunamäki, Nokia

  29. 802.11 DS WLAN interference Jukka Reunamäki, Nokia

  30. Blocking when RX IIP3  -30 dBm • How far away should a simultaneous transmission occur not to block the receiver? • Assumption: P1dB  IIP3 - 10 dB TX IEEE 802.11b WLAN TX transmitting at 20 dBm Another TX of the proposed system transmitting at -10 dBm Bluetooth TX transmitting at 0 dBm RX (IIP3  -30 dBm) 0 m 0.3 m 1 m 10 m Jukka Reunamäki, Nokia

  31. Frame structure and signal acquisition • Preamble should be long enough to assist frequency and symbol synchronization • Preferably zero DC • Sync word indicates the start of the header • 3 consecutive Barker codes of length 7 • Header and payload left to be defined in the MAC layer Preamble 32 bits Sync word 21 bits Header + payload + strong CRC's etc. (defined by MAC layer) Jukka Reunamäki, Nokia

  32. UP- CONVERSION LOWPASS FILTER DAC CHANNEL FILTER POWER AMPLIFIER + 0º LO 90º DAC TX implementation example Jukka Reunamäki, Nokia

  33. RX implementation example Jukka Reunamäki, Nokia

  34. Effect of finite I/Q image rejection Jukka Reunamäki, Nokia

  35. Power consumption estimates • RX analog/digital parts (active peak) 9.5 mW / 2.0 mW • Assuming NF = 15 dB, IIP3 = -30 dBm • TX analog/digital parts (active peak) 10.5 mW / 1.5 mW • Assuming Pout = -20 dBm • Total idle time power consumption (analog & digital) 22 W • Average consumption (based on 0.34% duty cycle) 60 W Jukka Reunamäki, Nokia

  36. Size and cost estimates • Total IC area ~ 6 mm2 • Package size (W x L x H) 6 x 6 x 1 mm3 • IC cost ~ $1 • External component count (SMD passives) 5...10 pcs • Size of SMD passives 0.5 x 1.0 x 0.5 mm3/pc • Module size (without antenna) 1 cm2 with components on both sides of PWB Jukka Reunamäki, Nokia

  37. Conclusions • Nokia IEEE 802.15.4 physical layer proposal comprising • Primarily operates in the 2.45 GHz ISM band, 1 MHz channel separation • 200 kbps maximum data rate, scalability achieved by means of packet sizing • Operation range from 1 to 10 meters • 2GFSK modulation with large modulation index • Spectrum efficiency, link performance and interference tolerance sacrificed for minimum power, minimum complexity PHY implementation Jukka Reunamäki, Nokia

  38. Self-evaluation against IEEE 802.15.4 criteria document (revision 4) Jukka Reunamäki, Nokia

  39. General solution criteria 1/3 Jukka Reunamäki, Nokia

  40. General solution criteria 2/3 Jukka Reunamäki, Nokia

  41. General solution criteria 3/3 Jukka Reunamäki, Nokia

  42. PHY Protocol Criteria Jukka Reunamäki, Nokia

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